Whistleblowing website Wikileaks has begun publishing the first of more than five million confidential emails from US-based intelligence company Stratfor.

The group said the documents would reveal Stratfor's "web of informers, pay-off structure, payment-laundering techniques and psychological methods".

Stratfor's computers were hacked by the activist group Anonymous in December.

Stratfor boss George Friedman said at the time anyone looking for signs of a vast conspiracy would be disappointed.

The firm warned ahead of the Wikileaks publication that it would make no comment on whether any of the emails were authentic or inaccurate.

"Having had our property stolen, we will not be victimised twice by submitting to questioning about them," Stratfor said in a statement.

'Shadow CIA'

Wikileaks did not say how it acquired the documents, but it is widely assumed to have been given them by the loose-knit hacker group Anonymous, which claimed to have stolen emails, passwords and credit-card details from the Texas-based firm in December.

Wikileaks said the emails date from July 2004 to the end of last year.

The first set of emails include messages suggesting US firm Dow Chemical had Stratfor monitor groups that campaigned for victims of the 1984 Bhopal gas tragedy in India.

Also in the files are emails involving a request by Coca-Cola for Stratfor to investigate animal rights group Peta ahead of the 2010 Vancouver Olympics, amid concerns by the drinks-maker that it could face protests by Peta activists.

What is Stratfor?

Founded in 1996, based in Austin, Texas

Provides geopolitical information and analysis through paid subscription and unique requests for individuals or companies

Does work by developing global network of human sources and analysing vast quantities of online data

Once likened, by the US weekly business magazine Barron's, to a "shadow CIA"

Grew in popularity after publishing analysis of Nato bombing in Kosovo

The whistleblowing website says it will release further emails in the coming days, promising evidence that the company's analysts had monitored Wikileaks itself.

"Here we have a private intelligence firm, relying on informants from the US government, foreign intelligence agencies with questionable reputations and journalists," Wikileaks founder Julian Assange told Reuters news agency.

"What is of grave concern is that the targets of this scrutiny are, among others, activist organisations fighting for a just cause."

Stratfor provides analysis of world affairs to subscribers which include major corporations, military officials and international government agencies.

The firm said in its statement that it had worked hard to build "good sources" in many countries, "as any publisher of global geopolitical analysis would do".

Despite the new disclosures, Wikileaks is still facing difficulties on several fronts.

The group admitted last October that it was running out of money.

Mr Assange is currently on conditional bail in Britain while he fights extradition to Sweden over sexual assault allegations, which he denies.